The present invention relates to a scanning mirror unit for scanning a beam which is used for obtaining observation images of the inside of a body cavity and for treating tissues etc. inside the body cavity, and a beam scanning probe which is equipped with the scanning mirror unit.
In surgical operations such as cranial nerve surgery using an endoscope (removal of a brain tumor, etc.) and intrauterine fetal surgery using a hysteroscope, high-precision intra-cavity operations (intra-body-cavity operations) using lasers are effective measures. For such operations, high-precision observation with high resolution is also required.
Intra-cavity operations, guiding a laser beam to the inside of a body cavity by an optical fiber, etc. and applying the laser beam to a tissue for incision, evaporation and conglutination, have been put into practice today. However, the irradiation range of the laser beam is generally wider than the core diameter of the optical fiber and it is difficult to treat tissues precisely. The irradiation range can be narrowed by converging the laser beam by use of a lens; however, it becomes necessary to move the tip of the optical fiber or probe in order to provide effective treatment. For mechanically moving the tip of the probe precisely, a complicated mechanism becomes necessary and it is difficult to ensure high reliability.
A beam converged by a lens can be scanned on a target (object) precisely by placing a microscanner between the lens and the focal point. For example, a type of confocal probe, observing a tissue by applying a laser beam to a tissue inside a body cavity and extracting particular reflected light (at a focal point of the objective optical system on the object side) from reflected light from the irradiated tissue, has been proposed and brought into practical use (see JP-A-11-221192 (pages 3–5, FIGS. 3–5), for example). Meanwhile, OCT (Optical Coherence Tomography) probes having the function of optical coherence tomography (obtaining a tomogram of the inside of a body cavity by use of light of low coherence) are also well known and in practical use today. An example of such a probe is disclosed in Japanese Patent Provisional Publication No. P2001-87269A.
The probes disclosed in the above patent documents are scanning probes which obtain 2-D images or 3-D images of a tissue (observation target) by scanning a laser beam emitted by a light source device on the tissue as the observation target by driving a microscanner.
However, the mirror used for such a scanner is generally thin and easily damaged in cases where a high power laser beam having high intensity effective for treatment of affected parts is scanned. The mirror of a microscanner (scanning mirror unit) formed by surface micromachining, etc. can not be thickened because of its manufacturing process.